Phase change inks

ABSTRACT

Disclosed is an ink composition comprising (a) a polyethylene homopolymer or copolymer binder having a melting point of from about 60 to about 150° C., (b) a nonpolymeric alcohol viscosity modifier having a melting point of from about 60 to about 150° C., (c) a colorant, (d) an optional conductivity enhancing agent, (e) an optional antioxidant, and (f) an optional UV absorber.

U.S. application Ser. No. 09/300,298, filed Apr. 27, 1999, entitled “InkCompositions,” with the named inventors Shadi L. Malhotra, Raymond W.Wong, and Marcel P. Breton, the disclosure of which is totallyincorporated herein by reference, discloses an ink compositioncomprising (1) an oxazoline compound; (2) a thiourea compound with anoptional melting point of from about 25 to about 100° C., and with anoptional acoustic loss value of from about 5 to about 40 dB/mm; (3) analcohol; (4) a lightfastness compound; (5) an antioxidant; and (6) acolorant.

U.S. application Ser. No. 09/300,331, filed Apr. 27, 1999, entitled “InkCompositions,” with the named inventors Marcel P. Breton, Shadi L.Malhotra, Raymond W. Wong, Danielle C. Boils, Carl P. Tripp, andPudupadi R. Sundararajan, the disclosure of which is totallyincorporated herein by reference, discloses an ink compositioncomprising (1) a solid oxazoline compound with a melting point of fromabout 60° C. to about 120° C. and an acoustic loss value of from about25 to about 80 dB/mm; (2) a carbamate compound with a melting point offrom about 25° C. to about 100° C.; (3) an alcohol compound; (4) alightfastness component; (5) a lightfastness antioxidant; and (6) acolorant.

BACKGROUND OF THE INVENTION

The present invention is directed to phase change (hot melt) inkcompositions. More specifically, the present invention is directed tophase change ink compositions suitable for use in ink jet printingprocesses, including piezoelectric ink jet printing processes, acousticink jet printing processes, and the like. One embodiment of the presentinvention is directed to an ink composition comprising (a) apolyethylene homopolymer or copolymer binder having a melting point offrom about 60 to about 150° C., (b) a nonpolymeric alcohol viscositymodifier having a melting point of from about 60 to about 150° C., (c) acolorant, (d) an optional conductivity enhancing agent, (e) an optionalantioxidant, and (f) an optional UV absorber.

Acoustic ink jet printing processes are known. In acoustic ink jetprinting processes, an acoustic beam exerts a radiation pressure againstobjects upon which it impinges. Thus, when an acoustic beam impinges ona free surface (i.e., liquid/air interface) of a pool of liquid frombeneath, the radiation pressure which it exerts against the surface ofthe pool may reach a sufficiently high level to release individualdroplets of liquid from the pool, despite the restraining force ofsurface tension. Focusing the beam on or near the surface of the poolintensifies the radiation pressure it exerts for a given amount of inputpower. These principles have been applied to prior ink jet and acousticprinting proposals. For example, K. A. Krause, “Focusing Ink Jet Head,”IBM Technical Disclosure Bulletin, Vol. 16, No. 4, September 1973, pp.1168-1170, the disclosure of which is totally incorporated herein byreference, describes an ink jet in which an acoustic beam emanating froma concave surface and confined by a conical aperture was used to propelink droplets out through a small ejection orifice. Acoustic ink printerstypically comprise one or more acoustic radiators for illuminating thefree surface of a pool of liquid ink with respective acoustic beams.Each of these beams usually is brought to focus at or near the surfaceof the reservoir (i.e., the liquid/air interface). Furthermore, printingconventionally is performed by independently modulating the excitationof the acoustic radiators in accordance with the input data samples forthe image that is to be printed. This modulation enables the radiationpressure which each of the beams exerts against the free ink surface tomake brief, controlled excursions to a sufficiently high pressure levelfor overcoming the restraining force of surface tension. That, in turn,causes individual droplets of ink to be ejected from the free inksurface on demand at an adequate velocity to cause them to deposit in animage configuration on a nearby recording medium. The acoustic beam maybe intensity modulated or focused/defocused to control the ejectiontiming, or an external source may be used to extract droplets from theacoustically excited liquid on the surface of the pool on demand.Regardless of the timing mechanism employed, the size of the ejecteddroplets is determined by the waist diameter of the focused acousticbeam. Acoustic ink printing is attractive because it does not requirethe nozzles or the small ejection orifices which have caused many of thereliability and pixel placement accuracy problems that conventional dropon demand and continuous stream ink jet printers have suffered. The sizeof the ejection orifice is a critical design parameter of an ink jetbecause it determines the size of the droplets of ink that the jetejects. As a result, the size of the ejection orifice cannot beincreased, without sacrificing resolution. Acoustic printing hasincreased intrinsic reliability because there are no nozzles to clog. Aswill be appreciated, the elimination of the clogged nozzle failure modeis especially relevant to the reliability of large arrays of inkejectors, such as page width arrays comprising several thousand separateejectors. Furthermore, small ejection orifices are avoided, so acousticprinting can be performed with a greater variety of inks thanconventional ink jet printing, including inks having higher viscositiesand inks containing pigments and other particulate components. It hasbeen found that acoustic ink printers embodying printheads comprisingacoustically illuminated spherical focusing lenses can print preciselypositioned pixels (i.e., picture elements) at resolutions which aresufficient for high quality printing of relatively complex images. Ithas also been discovered that the size of the individual pixels printedby such a printer can be varied over a significant range duringoperation, thereby accommodating, for example, the printing of variablyshaded images. Furthermore, the known droplet ejector technology can beadapted to a variety of printhead configurations, including (1) singleejector embodiments for raster scan printing, (2) matrix configuredejector arrays for matrix printing, and (3) several different types ofpagewidth ejector arrays, ranging from single row, sparse arrays forhybrid forms of parallel/serial printing to multiple row staggeredarrays with individual ejectors for each of the pixel positions oraddresses within a pagewidth image field (i.e., singleejector/pixel/line) for ordinary line printing. Inks suitable foracoustic ink jet printing typically are liquid at ambient temperatures(i.e., about 25° C.), but in other embodiments the ink is in a solidstate at ambient temperatures and provision is made for liquefying theink by heating or any other suitable method prior to introduction of theink into the printhead. Images of two or more colors can be generated byseveral methods, including by processes wherein a single printheadlaunches acoustic waves into pools of different colored inks. Furtherinformation regarding acoustic ink jet printing apparatus and processesis disclosed in, for example, U.S. Pat. No. 4,308,547, U.S. Pat. No.4,697,195, U.S. Pat. No. 5,028,937, U.S. Pat. No. 5,041,849, U.S. Pat.No. 4,751,529, U.S. Pat. No. 4,751,530, U.S. Pat. No. 4,751,534, U.S.Pat. No. 4,801,953, and U.S. Pat. No. 4,797,693, the disclosures of eachof which are totally incorporated herein by reference. The use offocused acoustic beams to eject droplets of controlled diameter andvelocity from a free-liquid surface is also described in J. Appl. Phys.,vol. 65, no. 9 (May 1, 1989) and references therein, the disclosure ofwhich is totally incorporated herein by reference.

In acoustic ink printing processes, the printhead produces approximately2.2 picoliter droplets by an acoustic energy process. The ink underthese conditions preferably displays a melt viscosity of from about 1 toabout 25 centipoise at the jetting temperature. In addition, once theink has been jetted onto the printing substrate, the image thusgenerated preferably exhibits excellent crease properties, and isnonsmearing, waterfast, of excellent transparency, and of excellent fix.The vehicle preferably displays a low melt viscosity in the acoustichead while also displaying solid like properties after being jetted ontothe substrate. Since the acoustic head can tolerate temperaturestypically up to about 180° C., the vehicle for the ink preferablydisplays liquid-like properties (such as a viscosity of from about 1 toabout 25 centipoise) at a temperature of from about 75 to about 180° C.,and solidifies or hardens after being jetted onto the substrate suchthat the resulting image exhibits a hardness value of from about 0.1 toabout 0.5 millimeter (measured with a penetrometer according to the ASTMpenetration method D1321).

Ink jet printing processes that employ inks that are solid at roomtemperature and liquid at elevated temperatures are known. For example,U.S. Pat. No. 4,490,731, the disclosure of which is totally incorporatedherein by reference, discloses an apparatus for dispensing solid inksfor printing on a substrate such as paper. The ink vehicle is chosen tohave a melting point above room temperature so that the ink, which ismelted in the apparatus, will not be subject to evaporation or spillageduring periods of nonprinting. The vehicle selected possesses a lowcritical temperature to permit the use of the solid ink in a thermal inkjet printer. In hot melt ink jet printing processes employing thesephase change inks, the solid ink is melted by a heater in the printingapparatus and used as a liquid in a manner similar to that ofconventional piezoelectric or thermal ink jet printing. Upon contactwith the printing substrate, the molten ink solidifies rapidly, enablingthe dye to remain on the surface instead of being carried into the paperby capillary action, thereby enabling higher print density than isgenerally obtained with liquid inks. After the phase change ink isapplied to the substrate, freezing on the substrate resolidifies theink. When the printer employs a piezoelectric hot melt ink jet printingprocess, a plurality of ink jet nozzles is provided in a printhead. Apiezoelectric vibrating element is located in each ink channel upstreamfrom a nozzle so that the piezoelectric oscillations propel ink throughthe nozzle. After the phase change ink is applied to the substrate,freezing on the substrate resolidifies the ink.

In phase change printing processes, the ink preferably undergoes achange with temperature from a solid state to a liquid state in adesirably short period of time, typically in less than about 100milliseconds. One advantage of phase change inks is their ability toprint superior images on plain paper, since the phase change ink quicklysolidifies as it cools, and, since it is primarily waxy in nature, itdoes not normally soak into a paper medium.

Phase change inks also preferably exhibit a high degree of transparency,generally measured in terms of haze value of the ink. Transparent, lowhaze inks exhibit high gloss and high optical density compared to opaqueinks, although both may appear to be evenly colored.

The use of phase change inks in acoustic ink printing processes is alsoknown. U.S. Pat. No. 4,745,419 (Quate et al.), the disclosure of whichis totally incorporated herein by reference, discloses acoustic inkprinters of the type having a printhead including one or more acousticdroplet ejectors for supplying focused acoustic beams. The printercomprises a carrier for transporting a generally uniformly thick film ofhot melt ink across its printhead, together with a heating means forliquefying the ink as it nears the printhead. The droplet ejector orejectors are acoustically coupled to the ink via the carrier, and theiroutput focal plane is essentially coplanar with the free surface of theliquefied ink, thereby enabling them to eject individual droplets of inktherefrom on command. The ink, on the other hand, is moved across theprinthead at a sufficiently high rate to maintain the free surface whichit presents to the printhead at a substantially constant level. Avariety of carriers may be employed, including thin plastic and metallicbelts and webs, and the free surface of the ink may be completelyexposed or it may be partially covered by a mesh or perforated layer. Aseparate heating element may be provided for liquefying the ink, or thelower surface of the carrier may be coated with a thin layer ofelectrically resistive material for liquefying the ink by localizedresistive heating.

U.S. Pat. No. 5,541,627 (Quate), the disclosure of which is totallyincorporated herein by reference, discloses a method and apparatus forejecting droplets from the crests of capillary waves riding on the freesurface of a liquid by parametrically pumping the capillary waves withelectric fields from probes located near the crests. Crest stabilizersare beneficially used to fix the spatial locations of the capillary wavecrests near the probes. The probes are beneficially switchably connectedto an AC voltage supply having an output that is synchronized with thecrest motion. When the AC voltage is applied to the probes, theresulting electric field adds sufficient energy to the system so thatthe surface tension of the liquid is overcome and a droplet is ejected.The AC voltage is synchronized such that the droplet is ejected aboutwhen the electric field is near is minimum value. A plurality of dropletejectors are arranged and the AC voltage is switchably applied so thatejected droplets form a predetermined image on a recording surface. Thecapillary waves can be generated on the free surface of the liquid byusing acoustical energy at a level approaching the onset of dropletejection. The liquid used with the invention must also be attracted byan electric field.

Phase change inks used in acoustic ink printing processes alsopreferably exhibit a low acoustic loss value, typically below about 100decibels per millimeter. In addition, the ink vehicle preferably canfill the pores of a porous substrate, such as paper, and preferably hasa melting point of from about 80 to about 120° C.; this melting point,along with low acoustic loss, enables a minimization of energyconsumption. When the phase change inks are used in an electric fieldassisted acoustic ink printing process, the inks also are sufficientlyconductive to permit the transmission of electrical signals generated bythe electric field assisted acoustic ink jet printer: the inkspreferably exhibit a conductivity of from about 2 to about 9log(picomho/cm) (measured under melt conditions at about 150° C. byplacing an aluminum electrode in the molten ink and reading theresistivity output on a GenRad 1689 precision RLC Digibridge at afrequency of 1 kiloHertz). In general, the conductivity of a materialcan be measured in terms of the reciprocal of resistivity, which is thecapacity for electrical resistance. Further information regardingelectric field assisted acoustic ink printing processes is disclosed in,for example, U.S. application Ser. No. 09/280,717, filed Mar. 30, 1999,entitled “Method and Apparatus for Moving Ink Drops using an ElectricField and Transfuse Printing System Using the Same,” with the namedinventors John S. Berkes, Vittorio R. Castelli, Scott A. Elrod, GregoryJ. Kovacs, Meng H. Lean, Donald L. Smith, Richard G. Stearns, and JoyRoy, the disclosure of which is totally incorporated herein byreference, which discloses a method of forming and moving ink dropsacross a gap between a printhead and a print medium or intermediateprint medium in a marking device. The method includes generating anelectric field, forming the ink drops adjacent to the printhead, andcontrolling the electric field. The electric field is generated toextend across the gap. The ink drops are formed in an area adjacent tothe printhead. The electric field is controlled such that an electricalattraction force exerted on the formed ink drops by the electric fieldis the greatest force acting on the ink drops. The marking device can beincorporated into a transfuse printing system having an intermediateprint medium made of one or more materials that allow for lateraldissipation of electrical charge from the incident ink drops.

U.S. Pat. No. 4,751,528 (Spehrley, Jr. et al.), the disclosure of whichis totally incorporated herein by reference, discloses a hot melt inkjet system including a temperature-controlled platen provided with aheater and a thermoelectric cooler electrically connected to a heat pumpand a temperature control unit for controlling the operation of theheater and the heat pump to maintain the platen temperature at a desiredlevel. The apparatus also includes a second thermoelectric cooler tosolidify hot melt ink in a selected zone more rapidly to avoid offset bya pinch roll coming in contact with the surface of the substrate towhich hot melt ink has been applied. An airtight enclosure surroundingthe platen is connected to a vacuum pump and has slits adjacent to theplaten to hold the substrate in thermal contact with the platen.

U.S. Pat. No. 4,791,439 (Guiles), the disclosure of which is totallyincorporated herein by reference, discloses an ink jet apparatus for usewith hot melt ink having an integrally connected ink jet head andreservoir system, the reservoir system including a highly efficient heatconducting plate, such as aluminum, inserted within an essentiallynon-heat conducting reservoir housing. The reservoir system has asloping flow path between an inlet position and a sump from which ink isdrawn to the head, and includes a plurality of vanes situated upon theplate for rapid heat transfer.

U.S. Pat. No. 4,853,036 (Koike et al.) and U.S. Pat. No. 5,124,718(Koike et al.), the disclosures of each of which are totallyincorporated herein by reference, disclose an ink for ink-jet recordingwhich comprises a liquid composition essentially comprised of a coloringmatter, a volatile solvent having a vapor pressure of 1 mmHg or more at25° C., and a material being solid at room temperature and having amolecular weight of 300 or more; and prepared so as to satisfy formulaB₁/A₁≧3, assuming viscosity as A₁ cP at 25° C. measured when the contentof the solid material in said composition is 10 percent by weight, andassuming viscosity as B₁, cP at 25° C. measured when the content of thesolid material in said composition is 30 percent by weight. An ink-jetrecording process employing the above mentioned ink is also provided.

U.S. Pat. No. 5,006,170 (Schwarz et al.) and U.S. Pat. No. 5,122,187(Schwarz et al.), the disclosures of each of which are totallyincorporated herein by reference, disclose hot melt ink compositionssuitable for ink jet printing which comprise a colorant, a binder, and apropellant selected from the group consisting of hydrazine; cyclicamines; ureas; carboxylic acids; sulfonic acids; aldehydes; ketones;hydrocarbons: esters: phenols, amides; imides; halocarbons; urethanes:ethers; sulfones; sulfamides; sulfonamindes; phosphites; phosphonates;phosphates; alkyl sulfines; alkyl acetates; and sulfur dioxide. Alsodisclosed are hot melt ink compositions suitable for ink jet printingwhich comprise a colorant, a propellant, and a binder selected from thegroup consisting of rosin esters; polyamides: dimer acid amides; fattyacid amides; epoxy resins, fluid paraffin waxes; fluid microcrystallinewaxes; Fischer-Tropsch waxes; polyvinyl alcohol resins; polyols;cellulose esters; cellulose ethers; polyvinyl pyridine resins; fattyacids; fatty acid esters; poly sulfonamides; benzoate esters; long chainalcohols; phthalate plasticizers; citrate plasticizers; maleateplasticizers; sulfones; polyvinyl pyrrolidinone copolymers; polyvinylpyrrolidone/polyvinyl acetate copolymers; novalac resins; naturalproduct waxes; mixtures of linear primary alcohols and linear long chainamides; and mixtures of linear primary alcohols and fatty acid amides.In one embodiment, the binder comprises a liquid crystalline material.

U.S. Pat. No. 5,041,161 (Cooke et al.), the disclosure of which istotally incorporated herein by reference, discloses an ink jet ink whichis semi-solid at room temperature. The subject ink combines theadvantageous properties of thermal phase change inks and liquid inks.More particularly, the inks comprise vehicles, such as glyceryl esters,polyoxyethylene esters, waxes, fatty acids, and mixtures thereof, whichare semi-solid at temperatures between 20° C. and 45° C. The ink isimpulse jetted at an elevated temperature in the range of above 45° C.to about 110° C., at which temperature the ink has a viscosity of about10 to 15 centipoise. The subject inks exhibit controlled penetration andspreading, but do not remain on the surface of most substrates wherethey would be prone to burnishing, cracking or flaking. These inksfurther comprise 0.1 to 30 weight percent of a colorant system.

U.S. Pat. No. 5,111,220 (Hadimoglu et al.), the disclosure of which istotally incorporated herein by reference, discloses a method offabricating an acoustic ink printhead with an integrated liquid levelcontrol layer. With standard photolithographic techniques, acousticlenses and ink supply channels are defined in a substrate. Apertures arecreated in a spacer layer plate to define cavities to hold the inkreservoirs for each ejector. Corresponding alignment holes are also madein the substrate and in the spacer layer plate. With spheres matchingthe size of the alignment holes, the spheres engage the alignment holesto precisely align the apertures in the spacer layer plate with theacoustic lenses in the substrate. The plate and substrate are thenbonded for an integrated acoustic printhead with liquid level control bycapillary action.

U.S. Pat. No. 5,121,141 (Hadimoglu et al.), the disclosure of which istotally incorporated herein by reference, discloses an acoustic inkprinthead with an integrated liquid level control layer. A spacer layeris fixed to a substrate. Apertures are created in the spacer layer,which is then used as a mask, to define acoustic lenses and ink supplychannels in the substrate. The apertures in the spacer layer used todefine self-aligned acoustic lenses and to form the cavities to hold theink reservoirs for each ejector. The thickness of the spacer layer isset so that acoustic waves from the acoustic lens below are focused atthe free surface of the ink which maintains its level at the top of thespacer layer by capillary action.

U.S. Pat. No. 5,371,531 (Rezanka et al.), the disclosure of which istotally incorporated herein by reference, discloses a multi-colorink-jet printer in which a first partial image is created on a recordingmedium, and then a second partial image is created on the same recordingmedium after the first partial image is substantially dried. The firstpartial image comprises an ink which dries at a slower rate than that ofthe second partial image. In one embodiment, means are provided forheating the recording medium prior to the creation of the second partialimage.

U.S. Pat. No. 5,698,017 (Sacripante et al.), the disclosure of which istotally incorporated herein by reference, discloses an ink compositioncomprising a colorant and a vehicle component, and which vehiclecomponent comprises the condensation product of an organic acid and anamino alcohol.

U.S. Pat. No. 5,922,117 (Malhotra et al.), the disclosure of which istotally incorporated herein by reference, discloses an ink compositioncomprising (1) a liquid alcohol vehicle, (2) a solid alcohol compound,(3) a quaternary compound, (4) a lightfastness UV absorber, (5) alightfastness antioxidant, and (6) a colorant.

U.S. Pat. No. 6,066,200 (Breton et al.), the disclosure of which istotally incorporated herein by reference, discloses an ink compositioncomprising (1) a solid urea compound; (2) an alcohol, (3) alightfastness component; (4) a lightfast antioxidant: and (5) acolorant.

U.S. Pat. No. 6,071,333 (Breton et al.), the disclosure of which istotally incorporated herein by reference, discloses an ink compositioncontaining (1) a solid carbamate compound, (2) an alcohol compound witha melting point of from about 25° C. to about 90° C.; (3) alightfastness component, (4) a lightfastness antioxidant; and (5) acolorant.

While known compositions and processes are suitable for their intendedpurposes, a need remains for phase change inks that are suitable for hotmelt ink jet printing processes, such as hot melt piezoelectric ink jetprinting processes and the like. Further, a need remains for phasechange inks that are suitable for hot melt acoustic ink jet printingprocesses. Additionally, a need remains for phase change inks that, uponcooling, form images with desirable hardness values. There is also aneed for phase change inks that, upon cooling, form images that arerobust and abrasion resistant. In addition, there is a need for phasechange inks that form images compatible with a wide variety of printsubstrates, such as plain papers, coated papers, transparencies, and thelike. Further, there is a need for phase change inks that form images ofphotographic quality, particularly when printed on plain paper.Additionally, there is a need for phase change inks that generatewaterfast images. A need also remains for phase change inks thatgenerate lightfast images. In addition, a need remains for phase changeinks that generate high quality images on a wide variety of substrates,including plain paper. Further, a need remains for phase change inksthat generate fast-drying images. Additionally, a need remains for phasechange inks that generate high quality text images. There is also a needfor phase change inks that generate high quality graphics images. Inaddition, there is a need for phase change inks that form images whereinthe colorant is retained on the surface of the print substrate while theink vehicle can continue to spread throughout the substrate. Further,there is a need for phase change inks that generate images-with minimalfeathering. Additionally, there is a need for phase change inks thatexhibit minimal intercolor bleed when two inks of different colors areprinted adjacent to each other on a substrate. A need also remains forphase change inks that generate images with high image permanence. Inaddition, a need remains for phase change inks suitable for ink jetprinting processes wherein the substrate is heated prior to printing andis cooled to ambient temperature subsequent to printing (also known asheat and delay printing processes). Further, a need remains for phasechange inks that can generate images of desirably high optical densityvalues even when the inks contain relatively low colorantconcentrations. Additionally, a need remains for phase change inks that,when printed onto substrates, cause minimized curling of the substrate.There is also a need for phase change inks that exhibit desirable creaseresistance. In addition, there is a need for phase change inks thatgenerate images with desirably high transparency and projectionefficiency. Further, there is a need for phase change inks wherein thespeculate size of spherical ink crystals formed therein during coolingand solidification can be reduced from about 6 to 9 microns to about 2to 4 microns. Additionally, there is a need for phase change inkswherein the speculate size of spherical ink crystals formed thereinduring cooling and solidification can be reduced from about 6 to 9microns to about 1 to 3 micron when the inks further containcrystallinity inhibitors derived from, for example, low viscosityunsaturated aliphatic acid compounds. There is also a need for phasechange inks that, when incorporated into an ink jet printer, exhibitcontrolled jettability. In addition, there is a need for phase changeinks that generate images with excellent projection efficiency, with noneed for a post fusing step to achieve such efficiency. Further, thereis a need for phase change inks that generate images with desirably highwaterfastness values. Additionally, there is a need for phase changeinks that generate images with desirably high lightfastness values. Aneed also remains for phase change inks that exhibit desirable viscosityvalues at hot melt ink printing temperatures.

SUMMARY OF THE INVENTION

The present invention is directed to an ink composition comprising (a) apolyethylene homopolymer or copolymer binder having a melting point offrom about 60 to about 150° C., (b) a nonpolymeric alcohol viscositymodifier having a melting point of from about 60 to about 150° C., (c) acolorant, (d) an optional conductivity enhancing agent, (e) an optionalantioxidant, and (f) an optional UV absorber.

DETAILED DESCRIPTION OF THE INVENTION

Inks of the present invention contain a binder which is a homopolymer(including substituted homopolymers) or copolymer (including substitutedcopolymers) of polyethylene. The binder typically has a melting point ofat least about 60° C., preferably at least about 90° C., and morepreferably at least about 110° C., and typically has a melting point ofno more than about 150° C., preferably no more than about 135° C., andmore preferably no more than about 115° C., although the melting pointcan be outside of these ranges. In specific embodiments, the binder hasa hardness value of at least about 70, more preferably at least about80, and even more preferably at least about 90, with there being noupper limit on hardness, although the hardness value can be outside ofthese ranges. Copolymers can be random, alternating, block, graft, orthe like. The homopolymers and copolymers can be substituted withfunctional groups, including (but not limited to) one or more of alkylgroups, substituted alkyl groups, aryl groups, substituted aryl groups,arylalkyl and alkylaryl groups, substituted arylalkyl and alkylarylgroups, alkoxy groups, aryloxy groups, arylalkyloxy and alkylaryloxygroups, hydroxy groups, halogen atoms, amine groups, imine groups,ammonium groups, cyano groups, pyridine groups, pyridinium groups, ethergroups, aldehyde groups, ketone groups, carboxylic acid groups, estergroups, amide groups, carbonyl groups, thiocarbonyl groups, sulfategroups, sulfonate groups, sulfide groups, sulfoxide groups, phosphinegroups, phosphonium groups, phosphate groups, nitrile groups, mercaptogroups, nitro groups, nitroso groups, sulfone groups, acyl groups, acidanhydride groups, azide groups, mixtures thereof, and the like, whereintwo or more substituents can be joined together to form a ring. Examplesof suitable binders include (but are not limited to) (1) polyethylenemonoalcohols, of the general formula CH₃(CH₂CH₂)_(n)CH₂OH), wherein nrepresents the number of repeat —H₂CH₂—units, such as (a) where Mn=460;viscosity at 150° C.=3.2 centipoise; melting point=86° C.; hardnessvalue=73.3 (Aldrich 44,447-2),and (b) where Mn=700; viscosity at 150°C.=7.9 centipoise; melting point=110° C. (Aldrich 44,448-0); (2)polyethylene-block-poly(alkylene glycol)s, wherein the alkylene portionis ethylene, propylene, butylene,pentylene, or the like, includingpolyethylene-block-poly(ethyleneglycol)s, of the general formulaCH₃(CH₂CH₂)_(x)(OCH₂CH₂)_(y)OH, wherein x represents the number ofrepeat —CH₂CH₂—units and y represents the number of repeat—OCH₂CH₂—units, such as (a) where Mn=575; 20 percent by weight ethyleneoxide; melting point=91° C. (Aldrich 45,900-3), (b) where Mn=875; 20percent by weight ethylene oxide; melting point=106° C. (Aldrich45,899-6), (c) where Mn=920; 50 percent by weight ethylene oxide;melting point=105° C. (Aldrich 45,898-8), and (d) where Mn=1400; 50percent by weight ethylene oxide, melting point=106° C. (Aldrich45,896-1); (3) oxidized polyethylenes, such as those where Mn=1300;viscosity at 125° C.=225 centipoise (Aldrich 19,191-4); (4)polyethylenemonocarboxylic acids, of the general formula CH₃(CH₂CH₂)_(n)COOH,wherein n represents the number of repeat —CH₂CH₂—units, such as Aldrich40,706-2, melting point=108-110° C.; hardness value 78.7; (5) copolymersof polyethylene with unsaturated acids, such as acrylic acid,methacrylic acid, and the like, including poly(ethylene-co-acrylicacid)s, of the general formula CH₃(CH₂CH₂)_(x)(CH₂CH(COOH))_(y), whereinx represents the number of repeat —CH₂CH₂— units and y represents thenumber of repeat —CH₂CH(COOH)— units, including those with acrylic acidcontents of from about 5 to about 20 percent by weight, and the like, aswell as mixtures thereof.

The polyethylene homopolymer or copolymer binder is present in the inkin any desired or effective amount, typically at least about 5 percentby weight of the ink, preferably at least about 10percent by weight ofthe ink, and more preferably at least about 15 percent by weight of theink, and typically no more than about 30 percent by weight of the ink,preferably no more than about 25 percent by weight of the ink, and morepreferably no more than about 20 percent by weight of the ink, althoughthe amount can be outside of these ranges.

Inks of the present invention also contain a nonpolymeric alcoholviscosity modifier. The viscosity modifier typically has a melting pointof at least about 60° C., preferably at least about 80° C., and morepreferably at least about 100° C., and typically has a melting point ofno more than about 150° C., preferably no more than about 130° C., andmore preferably no more than about 115° C., although the melting pointcan be outside of these ranges. In embodiments wherein the ink of thepresent invention is to be used in an acoustic ink printing process, theviscosity modifier preferably (although not necessarily) has an acousticloss value of no more than about 60 decibels per millimeter (with therebeing no lower limit on acoustic loss value), although the acoustic lossvalue can be outside of this range. At ink jet operating temperatures,the viscosity modifier generally has a viscosity lower than that of thebinder. The viscosity modifier is also selected to be compatible withthe binder so that no phase separation between binder and viscositymodifier occurs after the ink has been jetted onto a recordingsubstrate. The alcohol compound can have one or more hydroxy groups.Examples of suitable viscosity modifiers include (but are not limitedto) (A) benzyl alcohol derivatives, such as (1) 2-hydroxybenzyl alcohol(Aldrich 16,695-29), (2) 4-hydroxybenzyl alcohol (Aldrich H2,080-6), (3)4-nitrobenzyl alcohol (Aldrich N1,282-1), (4) 4-hydroxy-3-methoxy benzylalcohol (Aldrich 17,553-6, hardness value of 83.4), (5)3-methoxy-4-nitrobenzyl alcohol (Aldrich 19,383-6), (6)2-amino-5-chlorobenzyl alcohol (Aldrich 33,953-9), (7)2-amino-5-methylbenzyl alcohol (Aldrich 33,298-4), (8)3-amino-2-methylbenzyl alcohol (Aldrich 33,420-0), (9)3-amino-4-methylbenzyl alcohol (Aldrich 33,532-0), (10)2(2-(aminomethyl)phenylthio) benzyl alcohol (Aldrich 34,631-4), (11)2,4,6-trimethylbenzyl alcohol(Aldrich 19,163-9), and the like, (B)diols, such as (1) 2-amino-2-methyl-1,3-propanediol (Aldrich A6,517-4),(2) 2-amino-1-phenyl-1,3-propanediol (Aldrich 24,888-6), (3)2,2-dimethyl-1-phenyl-1,3-propanediol (Aldrich 40,873-5, hardness valueof 75), (4) 2-bromo-2-nitro-1,3-propanediol (Aldrich 13,470-8), (5)3-tert-butylamino-1,2-propanediol (Aldrich 47,298-0), (6)1,1-diphenyl-1,2-propanediol (Aldrich 36,490-8), (7)1,4-dibromo-2,3-butanediol (Aldrich 23,757-4), (8)2,3-dibromo-1,4-butanediol (Aldrich 30,104-3), (9)2,3-dibromo-2-butene-1,4-diol (Aldrich 14,370-7), (10)1,1,2-triphenyl-1,2-ethanediol (Aldrich 36,743-5), and the like, (C)other alcohols, such as (1) 2-naphthalenemethanol (Aldrich 18,731-3),(2) 2-methoxy-1-naphthalenemethanol (Aldrich 44,293-3), (3) decafluorobenzhydrol (Aldrich 19,658-4), (4) 2-methylbenzhydrol (Aldrich18,996-0), (5) 1-benzeneethanol (Aldrich B,300-0), (6)4,4′-isopropylidene bis(2-(2,6-dibromo phenoxy)ethanol) (Aldrich19,443-3), (7) (2,2′-(1,4-phenylenedioxy)diethanol) (Aldrich 23,791-4,hardness value of 82), (8)2,2-bis(hydroxymethyl)-2,2′,2″-nitrilotriethanol (Aldrich 15,666-3,hardness value of 82.2), (9) di(trimethylolpropane) (Aldrich 41,613-4,hardness value of 85.8), (10) 2-amino-3-phenyl-1-propanol(Aldrich19,043-8), (11) tricyclohexylmethanol (Aldrich 18,058-0), (12)tris(hydroxymethyl)aminomethane succinate (Aldrich 34,068-5), (13)4,4′-trimethylene bis(1-piperidine ethanol) (Aldrich 12,122-35, hardnessvalue of 78), (14) N-methyl glucamine (Aldrich M4,700-0, hardnessvalueof 83.2), (15) xylitol (Aldrich 85,158-2), and the like; and thelike, as well as mixtures thereof.

The nonpolymeric alcohol viscosity modifier is present in the ink in anydesired or effective amount, typically at least about 30 percent byweight of the ink, preferably at least about 35 percent by weight of theink, and more preferably at least about 40 percent by weight of the ink,and typically no more than about 55 percent by weight of the ink,preferably no more than about 50 percent by weight of the ink, and morepreferably no more than about 45 percent by weight of the ink, althoughthe amount can be outside of these ranges.

The inks of the present invention also contain a colorant. Any desiredor effective colorant can be employed in the inks of the presentinvention, including dyes, pigments, mixtures thereof, and the like,provided that the colorant can be dissolved or dispersed in the inkvehicle. The colorant is present in the ink in any desired or effectiveamount to obtain the desired color and hue, typically at least about1percent by weight of the ink, and preferably at least about 5 percentby weight of the ink, and typically no more than about 15 percent byweight of the ink, and preferably no more than about 10 percent byweight of the ink, although the amount can be outside of these ranges.

Examples of suitable pigments include (but are not limited to) VioletToner VT-8015 (Paul Uhlich); Paliogen Violet 5100 (BASF); PaliogenViolet 5890 (BASF); Permanent Violet VT 2645 (Paul Uhlich); HeliogenGreen L8730 (BASF); Argyle Green XP-111-S (Paul Uhlich): Brilliant GreenToner GR 0991 (Paul Uhlich); Lithol Scarlet D3700 (BASF); Toluidine Red(Aldrich); Scarlet for Thermoplast NSD PS PA (Ugine Kuhlmann of Canada);E.D. Toluidine Red (Aldrich); Lithol Rubine Toner (Paul Uhlich); LitholScarlet 4440 (BASF); Bon Red C (Dominion Color Company); Royal BrilliantRed RD-8192 (Paul Uhlich); Oracet Pink RF (Ciba-Geigy): Paliogen Red3871K (BASF), Paliogen Red 3340 (BASF): Lithol Fast Scarlet L4300(BASF): Heliogen Blue L6900, L7020 (BASF): Heliogen Blue K6902, K6910(BASF); Heliogen Blue D6840, D7080 (BASF); Sudan Blue OS (BASF); NeopenBlue FF4012 (BASF); PV Fast Blue B2G01 (American Hoechst); Irgalite BlueBCA (Ciba-Geigy); Paliogen Blue 6470 (BASF); Sudan III (Red Orange)(Matheson, Colemen Bell); Sudan II (Orange) (Matheson, Colemen Bell);Sudan Orange G (Aldrich); Sudan Orange 220 (BASF); Paliogen Orange 3040(BASF); Ortho Orange OR 2673 (Paul Uhlich); Paliogen Yellow 152, 1560(BASF); Lithol Fast Yellow 0991K (BASF); Paliotol Yellow 1840 (BASF);Novoperm Yellow FGL (Hoechst), Permanent Yellow YE 0305 (Paul Uhlich),Lumogen Yellow D0790 (BASF); Suco-Yellow L1250 (BASF); Suco-Yellow DI355 (BASF); Suco Fast Yellow D1355, D1351 (BASF); Hostaperm Pink E(American Hoechst); Fanal Pink D4830 (BASF); Cinquasia Magenta (DuPont), Paliogen Black L0084 (BASF); Pigment Black K801 (BASF); andcarbon blacks such as REGAL 330® (Cabot), Carbon Black 5250, CarbonBlack 5750 (Columbia Chemical), and the like.

Examples of suitable dyes include (but are not limited to) Pontamine;Food Black 2; Carodirect Turquoise FBL Supra Conc. (Direct Blue 199),available from Carolina Color and Chemical; Special Fast Turquoise 8 GLLiquid (Direct Blue 86), available from Mobay Chemical; Intrabond LiquidTurquoise GLL (Direct Blue 86), available from Crompton and Knowles;Cibracron Brilliant Red 38-A (Reactive Red 4), available from AldrichChemical; Drimarene Brilliant Red X-2B (Reactive Red 56), available fromPylam, Inc.; Levafix Brilliant Red E-4B, available from Mobay Chemical;Levafix Brilliant Red E6BA, available from Mobay Chemical; Procion RedH8B (Reactive Red 31), available from ICI America; Pylam Certified D&CRed #28 (Acid Red 92), available from Pylam; Direct Brill Pink B GroundCrude, available from Crompton and Knowles; Cartasol Yellow GTFPresscake, available from Sandoz, Inc.; Tartrazine Extra Conc. (FD&CYellow #5, Acid Yellow 23), available from Sandoz, Inc.; CarodirectYellow RL (Direct Yellow 86), available from Carolina Color andChemical; Cartasol Yellow GTF Liquid Special 110, available from Sandoz,Inc., D&C Yellow #10 (Acid Yellow 3), available from Tricon; YellowShade 16948, available from Tricon; Basacid Black X 34, available fromBASF, Carta Black 2GT, available from Sandoz, Inc.; and the like. Alsosuitable are solvent dyes, including (but not limited to) spirit solubledyes. Examples of suitable spirit solvent dyes include (but are notlimited to) Neozapon Red 492 (BASF); Orasol Red G (Ciba-Geigy); DirectBrilliant Pink B (Crompton & Knowles); Aizen Spilon Red C-BH (HodogayaChemical): Kayanol Red 3BL (Nippon Kayaku); Levanol Brilliant Red 3BW(Mobay Chemical); Levaderm Lemon Yellow (Mobay Chemical); Spirit FastYellow 3G; Aizen Spilon Yellow C-GNH (Hodogaya Chemical); Sirius SupraYellow GD 167; Cartasol Brilliant Yellow 4GF (Sandoz); Pergasol YellowCGP (Ciba-Geigy); Orasol Black RLP (Ciba-Geigy); Savinyl Black RLS(Sandoz), Dermacarbon 2GT (Sandoz); Pyrazol Black BG (ICI); MorfastBlack Conc. A (Morton-Thiokol); Diaazol Black RN Quad (ICI); Orasol BlueGN (Ciba-Geigy); Savinyl Blue GLS (Sandoz); Luxol Blue MBSN(Morton-Thiokol); Sevron Blue 5GMF (ICI); Basacid Blue 750 (BASF):Brilliant Red F3B-SF VP-218 (Hoechst Celanese), and the like.

The inks of the present invention can also optionally contain aconductivity enhancing agent. The conductivity enhancing agentpreferably is nonpolymeric. Examples of suitable conductivity enhancingagents include complexes of amines with sulfur-containing acids or acidsalts and complexes of amines with phosphorus-containing compounds, withexamples of amines including (a) alkyl amines, such as (1)4-(hexadecylamino)benzylamine (Aldrich 38,966-8), (2)N-octanoyl-N-methyl-glucamine (Aldrich 34,389-7), (3) octanoic hydrazide(Aldrich 29,334-2), and the like; (b) anilines, such as (1) 4-hexadecylsulfonyl aniline (Aldrich 14,338-3), and the like; (c) dianiline and bisdianiline compounds, such as (1) 2,2′-dithio dianiline (Aldrich16,676-6), (2) 4,4′-dithiodianiline (Aldrich 36,946-26), (3)3,3′-methylene dianiline (Aldrich 37,826-7), (4) 4,4′-methylenedianiline (Aldrich 13,245-4), (5) N-methyl-4,4′-methylene dianiline(Aldrich 42,282-7), (6) 4,4′-methylene bis(2,6-diethyl aniline) (Aldrich36,078-3), (7) 4,4′-methylene bis(2,6-diisopropyl-N,N-dimethylaniline)(Aldrich 40,353-9), (8) 4,4′-methylene bis(N,N-dimethylaniline) (AldrichM4,445-1), (9) 4,4′-methylene bis(2,6-dimethylaniline) (Aldrich36,079-1), (10) 4,4-methylene bis(3-chloro-2,6-diethylaniline) (Aldrich42,660-1), (11) 3,3′-(sulfonyl bis(4,1-phenylene))dianiline (Aldrich44,095-7), (12) 4,4′-(1,3-phenylene diisopropylidene) bisaniline(Aldrich 45,048-0), and the like; and the like, as well as mixturesthereof. Examples of suitable sulfur-containing acids and acid saltswith which the amines can be complexed include (1) 2,4-dinitrobenzenesulfonic acid dihydrate (Aldrich 38,106-3), (2) 2-propanesulfonic acid,sodium salt monohydrate (Aldrich 39,701-6), (3) p-toluenesulfonic acidmonohydrate (Aldrich 40,288-5), (4) hydroxymethane sulfinic acid monosodium salt dihydrate (Aldrich 16,351-1), and the like, as well asmixtures thereof. Examples of conductivity inducing phosphorouscompounds with which the amines can be complexed includephosphorus-containing acid compounds, with specific examples including(1) phenylphosphinic acid (Aldrich P2,880-8), (2) dimethylphosphinicacid (Aldrich 32,829-4), (3) methyl phosphonic acid (Aldrich 28,986-8),and the like, as well as mixtures thereof. The amine and thephosphorus-containing compound or sulfur-containing acid or acid saltare present in any desired or effective amount with respect to eachother, typically from about 0.3 mole of amine per every one mole ofsulfur-containing acid or acid salt to about 3 moles of amine per everyone mole of sulfur-containing acid or acid salt, although the relativeamounts can be outside of this range.

Also suitable are conductivity enhancing agents such as (1) acetylcholine chloride (CH₃COOCH₂CH₂N(CH₃)₃Cl, Aldrich 13,535-6), (2) acetylcholine bromide (CH₃COOCH₂CH₂N(CH₃)₃Br; Aldrich 85,968-0), (3)acetyl-β-methyl choline bromide (CH₃COOCH(CH₃)CH₂N(CH₃)₃Br, Aldrich85,554-5), (4) (diethyl-(4-aminobenzyl)Phosphonate (Aldrich 33,847-8),(5) diethyl-(phthalimidomethyl)Phosphonate (Aldrich 36,622-6), (6)diethyl-(2,2,2-trifluoro-1-hydroxyethyl)Phosphonate (Aldrich 43,982-7),(7) diphenyl succinimidyl phosphate (Aldrich 45,061-8), (8) dihexadecylphosphate (Aldrich 27,149-7), (9) undecylenic acid zinc salt (hardnessvalue 68; Aldrich 32,958-4), (10)zincbis(2,2,6,6-tetramethy(-3,5-heptanedionate) (Aldrich 41,773-4), (11)zinccyclohexanebutyrate (Aldrich 22,841-9), (12) zinc stearate (Aldrich30,756-4), (13) methyl-1-adamantane sulfonate (Aldrich 40,956-1), (14)octadecyl-4-chlorobenzene sulfonate (Aldrich 47,799-0), (15)tetrabutylammonium trifluoromethanesulfonate (Aldrich 34,509-1), (16)S,S′-ethylene-p-toluene thiosulfonate (Aldrich 23,257-2), (17)pyridinium-3-nitrobenzene sulfonate (Aldrich 27,198-5), (18)trimethylsulfonium methyl sulfate (Aldrich 30,359-3), (19) 1-(p-toluenesulfonyl)imidazole (Aldrich 24,424-4), (20) 1-(p-toluenesulfonyl)-3-nitro-1,2,4-triazole (Aldrich 24,417-1), (21)2,4,6-triisopropyl benzene sulfonyl chloride (Aldrich 11,949-0), (22)1-(2,4,6-triisopropyl benzene sulfonyl)imidazole (Aldrich 40,948-0),(23) 1-(2,4,6-triisopropyl benzene sulfonyl)-3-nitro-1,2,4-triazole(Aldrich 40,948-0), (24) 4-nitrobenzene sulfonyl chloride (Aldrich27,224-8), (25) perfluoro decyl iodide (Aldrich 25,784-2), (26)1,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8-heptadeca fluoro-10-iododecane(Aldrich 37,052-5), and the like, as well as mixtures thereof.

The optional conductivity enhancing agent, when present, is present inthe ink in any desired or effective amount, typically at least about 4percent by weight of the ink, and preferably at least about 15 percentby weight of the ink, and typically no more than about 40 percent byweight of the ink, and preferably no more than about 35 percent byweight of the ink, although the amount can be outside of these ranges.

Optionally, the inks of the present invention can also contain anantioxidant. The optional antioxidants in the inks protect the imagesfrom oxidation and also protect the ink components from oxidation duringthe heating portion of the ink preparation process. Specific examples ofsuitable antioxidants include (but are not limited to) (1)N,N′-hexamethylene bis(3,5-di-tert-butyl-4-hydroxy hydrocinnamamide)(Irganox 1098, available from Ciba-Geigy Corporation), (2)2,2-bis(4-(2-(3,5-di-tert-butyl-4-hydroxyhydrocinnamoyloxy))ethoxyphenyl)propane(Topanol-205, available from ICI America Corporation), (3)tris(4-tert-butyl-3-hydroxy-2,6-dimethyl benzyl)isocyanurate (Cyanox1790, 41,322-4, LTDP, Aldrich D12,840-6), (4) 2,2′-ethylidenebis(4,6-di-tert-butylphenyl)fluoro phosphonite (Ethanox-398, availablefrom Ethyl Corporation), (5)tetrakis(2,4-di-tert-butylphenyl)-4,4′-biphenyl diphosphonite (Aldrich46,852-5; hardness value 90), (6) pentaerythritol tetrastearate (TCIAmerica #P0739), (7) tributylammonium hypophosphite (Aldrich 42,009-3),(8) 2,6-di-tert-butyl-4-methoxyphenol (Aldrich 25,106-2), (9)2,4-di-tert-butyl-6(4-methoxybenzyl)phenol (Aldrich 23,008-1), (10)4-bromo-2,6-dimethylphenol (Aldrich 34,951-8), (11)4-bromo-3,5-didimethylphenol (Aldrich B6,420-2), (12)4-bromo-2-nitrophenol (Aldrich 30,987-7), (13) 4-(diethylaminomethyl)-2,5-dimethylphenol (Aldrich 14,668-4), (14)3-dimethylaminophenol (Aldrich D14,400-2), (15)2-amino-4-tert-amylphenol (Aldrich 41,258-9), (16)2,6-bis(hydroxymethyl)-p-cresol (Aldrich 22,752-8), (17)2,2′-methylenediphenol (Aldrich B4,680-8), (18)5-(diethylamino)-2-nitrosophenol (Aldrich 26,951-4), (19)2,6-dichloro-4-fluorophenol (Aldrich 28,435-1), (20) 2,6-dibromo fluorophenol (Aldrich 26,003-7), (21) α,α,α-trifluoro-o-cresol (Aldrich21,979-7), (22) 2-bromo-4-fluorophenol (Aldrich 30,246-5), (23)4-fluorophenol (Aldrich F1,320-7), (24)4-chlorophenyl-2-chloro-1,1,2-trifluoroethyl sulfone (Aldrich 13,823-1),(25) 3,4-difluoro phenylacetic acid (Aldrich 29,043-2), (26)3-fluorophenylacetic acid (Aldrich 24,804-5), (27) 3,5-difluorophenylacetic acid (Aldrich 29,044-0), (28) 2-fluorophenylacetic acid(Aldrich 20,894-9), (29) 2,5-bis(trifluoromethyl)benzoic acid (Aldrich32,527-9), (30) ethyl-2-(4-(4-(trifluoromethyl)phenoxy)phenoxy)propionate (Aldrich 25,074-0), (31) tetrakis(2,4-di-tert-butylphenyl)-4,4′-biphenyl diphosphonite (Aldrich 46,852-5), (32) 4-tert-amylphenol (Aldrich 15,384-2), (33) 3-(2H-benzotriazol-2-yl)-4-hydroxyphenethylalcohol (Aldrich 43,071-4), and the like, as well as mixturesthereof.

The optional antioxidant, when present, is present in the ink in anydesired or effective amount, typically at least about 0.25 percent byweight of the ink, and preferably at least about 1 percent by weight ofthe ink, and typically no more than about 10 percent by weight of theink, and preferably no more than about 5 percent by weight of the ink,although the amount can be outside of these ranges.

The inks of the present invention can also optionally contain a UVabsorber. The optional UV absorbers primarily protect the imagesgenerated therewith from UV degradation. Specific examples of suitableUV absorbers include (1) 2-bromo-2′,4-dimethoxyacetophenone (Aldrich19,948-6), (2) 2-bromo-2′,5′-dimethoxyacetophenone (Aldrich 10,458-2),(3) 2-bromo-3′-nitroacetophenone (Aldrich 34,421-4), (4)2-bromo-4′-nitroacetophenone (Aldrich 24,561-5), (5)3′,5′-diacetoxyacetophenone (Aldrich 11,738-2), (6) 2-phenylsulfonylacetophenone (Aldrich 34,150-3), (7) 3′-aminoacetophenone (Aldrich13,935-1), (8) 4′-aminoacetophenone (Aldrich A3,800-2), (9)1H-benzotriazole-1-acetonitrile (Aldrich 46,752-9), (10)2-(2H-benzotriazol-2-yl)-4,6-di-tert-pentylphenol (Aldrich 42,274-6),(11) 1,1-(1,2-ethane-diyl)bis(3,3,5,5-tetramethylpiperazinone)(commercially, available from Goodrich Chemicals), (12)2,2,4-trimethyl-1,2-hydroquinoline (commercially available from MobayChemical), (13) 2-(4-benzoyl-3-hydroxy phenoxy)ethylacrylate, (14)2-dodecyl-N-(1,2,2,6,6-pentamethyl-4-piperidinyl)succinimide(commercially available from Aldrich Chemical Co., Milwaukee, Wis.),(15)2,2,6,6-tetramethyl-4-piperidinyl/β,β,β′,β′-tetramethyl-3,9-(2,4,8,10-tetraoxospiro(5,5)-undecane) diethyl-1,2,3,4-butane tetracarboxylate(commercially available from Fairmount), (16)N-(p-ethoxycarbonylphenyl)-N′-ethyl-N′-phenylformadine (commerciallyavailable from Givaudan), (17)6-ethoxy-1,2-dihydro-2,2,4-trimethylquinoline (commercially availablefrom Monsanto Chemicals), (18)2,4,6-tris-(N-1,4-dimethylpentyl-4-phenylenediamino)-1,3,5-triazine(commercially available from Uniroyal), (19)2-dodecyl-N-(2,2,6,6-tetramethyl-4-piperidinyl) succinimide(commercially available from Aldrich Chemical Co.), (20)N-(1-acetyl-2,2,6,6-tetramethyl-4-piperidinyl)-2-dodecyl succinimide(commercially available from Aldrich Chemical Co.), (21)(1,2,2,6,6-pentamethyl-4-piperidinyl/β,ββ′,β′-tetramethyl-3,9-(2,4,8,10-tetraoxo-spiro-(5,5) undecane)diethyl)-1,2,3,4-butanetetracarboxylate(commercially available from Fairmount), (22)(2,2,6,6-tetramethyl-4-piperidinyl)-1,2,3,4-butane tetracarboxylate(commercially available from Fairmount), (23) nickel dibutyl dithiocarbamate (commercially available as UV-Chek AM-105 from Ferro), (24)2-amino-2′,5-dichlorobenzophenone (Aldrich 10,515-5), (25)2′-amino-4′,5′-dimethoxyacetophenone (Aldrich 32,922-3), (26)2-benzyl-2-(dimethylamino)-4′-morpholino butyrophenone (Aldrich40,564-7), (27) 4′-benzyloxy-2′-hydroxy-3′-methylacetophenone (Aldrich29,884-0), (28) 4,4′-bis(diethylamino)benzophenone (Aldrich 16,032-6),(29) 5-chloro-2-hydroxy benzophenone (Aldrich C4,470-2), (30)4′-piperazinoacetophenone (Aldrich 13,646-8), (31)4′-piperidinoacetophenone (Aldrich 11,972-5), (32)2-amino-5-chlorobenzophenone (Aldrich A4,556-4), (33)3,6-bis(2-methyl-2-morpholinopropionyl)-9-octylcarbazole (Aldrich46,073-7), and the like, as well as mixtures thereof.

When present, the optional UV absorber is present in the ink in anydesired or effective amount, typically at least about 1 percent byweight of the ink, and preferably at least about 3 percent by weight ofthe ink, and typically no more than about 10 percent by weight of theink, and preferably no more than about 5 percent by weight of the ink,although the amount can be outside of these ranges.

The inks of the present invention can be prepared by any suitablemethod, such as by simple mixing of the ink components, followed byheating to a temperature of, for example, about 140° C. and stirringfor, for example, about 60 minutes until a homogeneous solution hasformed, followed by cooling to about 25° C.

The ink compositions of the present invention typically have meltingpoints no lower than about 60° C., and preferably no lower than about90° C., and typically have melting points no higher than about 150° C.,and preferably no higher than about 120° C., although the melting pointcan be outside of these ranges.

In embodiments wherein the ink compositions of the present invention areused in acoustic ink printing processes, the inks generally have meltviscosities at the jetting temperature (typically no lower than about75° C., preferably no lower than about 100° C., and more preferably nolower than about 120° C., and typically no higher than about 180° C.,preferably no higher than about 150° C., and more preferably no higherthan about 130° C., although the jetting temperature can be outside ofthese ranges) typically of no more than about 25 centipoise, preferablyno more than about 20 centipoise, and even more preferably no more thanabout 10 centipoise, and typically of no less than about 2 centipoise,preferably no less than about 5 centipoise, and even more preferably noless than about 7 centipoise, although the melt viscosity can be outsideof these ranges. Higher melt viscosities are suitable for piezoelectricink jet printing processes. Since image hardness tend to drop with lowerviscosities, it is preferred that the viscosity be as low as possiblewhile still retaining the desired degree of image hardness.

Hardness is a property of solids and plastics that is defined by theirsolidity and firmness as measured by their resistance to indentation byan indenter of fixed shape and size under a static load. The hardness ofimages can be measured with a Digital-Pencil style Durometer, Model211B-00 PTC, obtained from Pacific Transducer Corporation, using ASTMStandard specifications for resistance to penetration with a conical (30degrees included angle) indenter and applying a 1 kilogram load. Thehardness range for materials as measured with this instrument is fromabout 1 to about 100, the latter being the highest measurable value. Itis believed that the images generated with the inks of the presentinvention, after cooling to ambient temperature (typically from about 20to about 25° C., although ambient temperature can be outside of thisrange) will exhibit hardness values of at least about 70 or more, and insome embodiments will exhibit hardness values of about 80 or about 85.

In embodiments wherein the inks of the present invention are employed inacoustic ink printing processes, the inks typically undergo, uponheating, a change from a solid state to a liquid state in a period ofless than about 100 milliseconds, preferably less than about 50milliseconds, and more preferably less than about 10 milliseconds,although the time can be outside of these ranges. There is no necessarylower limit on this period of time for the inks; it is believed thatpractically achievable lower limits are around 5 milliseconds, although,if practically achievable, lower periods of time are acceptable.

When used in acoustic ink printing applications, the inks of the presentinvention typically exhibit acoustic loss values of no more than about100 decibels per millimeter, preferably no more than about 60 decibelsper millimeter, and more preferably no more than about 40 decibels permillimeter, although the acoustic loss value can be outside of theseranges. There is no necessary lower limit on acoustic loss value for theinks; it is believed that practically achievable lower limits are around10 decibels per millimeter, although, if practically achievable, loweracoustic loss values are acceptable. Acoustic loss can be measured byplacing a sample of the material to be measured between two transducerswith the temperature set at about 150° C. The samples are allowed toequilibrate at 150° C. for five minutes. The two transducers are thenbrought together to maximize the acoustic signal. The amplitude and theposition of the signals are recorded. The two transducers are thenseparated by a distance varying from about 25.4 microns to about 125.4microns, recording each time the amplitude and the position of thesignal. Preferably, each measurement is performed three times, and threesamples of the same material are measured. The attenuation decibels permillimeter is then calculated by ratioing the amplitude values obtainedat different separation distances.

The inks of the present invention typically exhibit a conductivity of noless than about 2 log(picomho/cm), preferably no less than about 6log(picomho/cm), and more preferably no less than about 6.5log(picomho/cm), and even more preferably no less than about 7log(picomho/cm), although the conductivity can be outside of theseranges. While there is no upper limit on conductivity, typicalconductivity values generally do not exceed about 9 log(picomho/cm).Conductivity can be measured under melt conditions (typically at about150° C.) by placing an aluminum electrode in the molten ink and readingthe resistivity output on a GenRad 1689 precision RLC Digibridge at afrequency of 1 kiloHertz. The conductivity of the material is measuredin terms of the reciprocal of resistivity, which is the capacity forelectrical resistance.

The inks of the present invention exhibit substantial transparency. Theimages generated with the inks typically exhibit haze values of no morethan about 25, preferably no more than about 15, and more preferably nomore than about 10, although the haze value can be outside of theseranges. There is no required lower limit on haze values. Haze values canbe measured on images printed with the ink on uncoated polyester, suchas MYLAR®, with a Haze meter XL-211, HAZEGARD® System obtained fromPacific Scientific Company.

The inks of the present invention generate images with desirable creaseresistance. The images generated with the inks typically exhibit creasevalues of no more than about 0.6 millimeters, preferably no more thanabout 0.2 millimeters, and more preferably no more than about 0.1millimeters, although the crease value can be outside of these ranges.There is no lower limit on crease values; ideally, this value is zero.The average width of the creased image can be measured by printing animage on paper, followed by (a) folding inwards the printed area of theimage, (b) passing over the folded image a standard TEFLON® coatedcopper roll 2 inches in width, 3 inches in outer diameter, 2.25 inchesin inner diameter, and weighing 860 grams, (c) unfolding the paper andwiping the loose ink from the creased imaged surface with a cotton swab,and (d) measuring the average width of the ink free creased area with animage analyzer. The crease value can also be reported in terms of area,especially when the image is sufficiently hard to break unevenly oncreasing. Measured in terms of area, crease values of 60 millimeterscorrespond to about 0.6, crease values of 40 millimeters correspond toabout 0.4, crease values of 10 millimeters correspond to about 0.1, andthe like.

Any suitable print substrate or recording sheet can be employed,including plain papers such as Xerox® 4024 papers, Xerox® Image Seriespapers, Courtland 4024 DP paper, ruled notebook paper, bond paper,silica coated papers such as Sharp Company silica coated paper, JuJopaper, and the like, transparency materials, fabrics, textile products,plastics, polymeric films, inorganic substrates such as metals and wood,and the like. In a preferred embodiment, the process entails printingonto a porous or ink absorbent substrate, such as plain paper.

The inks of the present invention are particularly suitable for printingprocesses wherein the print substrate, such as paper, transparencymaterial, or the like, is heated during the printing process tofacilitate formation of the liquid crystalline phase within the ink.When transparency substrates are employed, temperatures typically arelimited to a maximum of about 100° C. to about 110° C., since thepolyester typically employed as the base sheet in transparency sheetstends to deform at higher temperatures. Specially formulatedtransparencies and paper substrates can, however, tolerate highertemperatures, and frequently are suitable for exposure to temperaturesof 150° C. or even 200° C. in some instances.

The present invention is also directed to a process which entailsincorporating an ink of the present invention into an ink jet printingapparatus, melting the ink, and causing droplets of the melted ink to beejected in an imagewise pattern onto a print substrate. In one specificembodiment, the printing apparatus employs an acoustic ink jet process,wherein droplets of the ink are caused to be ejected in imagewisepattern by acoustic beams. In another specific embodiment, the printingapparatus employs an acoustic ink jet printing process wherein dropletsof the ink are formed by acoustic beams without imparting a substantialvelocity component toward the print substrate, using a droplet formingforce that is sufficient only to form the ink droplets, and the printingprocess further comprises generating an electric field to exert anelectrical force different from the droplet forming force on the inkdroplets to move the ink droplets toward the print substrate, andcontrolling the electrical force exerted on the formed complete inkdroplets by the electric field. The inks of the present invention arealso suitable for piezoelectric ink jet printing processes, wherein theprinting process entails incorporating the ink into an ink jet printingapparatus, melting the ink, and causing droplets of the melted ink to beejected in an imagewise pattern onto a print substrate, wherein theprinting apparatus employs a piezoelectric ink jet process, whereindroplets of the ink are caused to be ejected in imagewise pattern byoscillations of piezoelectric vibrating elements.

Specific embodiments of the invention will now be described in detail.These examples are intended to be illustrative, and the invention is notlimited to the materials, conditions, or process parameters set forth inthese embodiments. All parts and percentages are by weight unlessotherwise indicated.

Acoustic loss measurements in the Examples were measured by placingsamples of the materials between the two transducers with thetemperature set at 150° C. The samples were allowed to equilibrate at150° C. for five minutes. The two transducers were then brought togetherto maximize the acoustic signal. The amplitude and the position of thesignals were recorded. The two transducers were then separated by adistance varying from 25.4 microns to 125.4 microns, recording each timethe amplitude and the position of the signal. Each measurement wasperformed three times, and three samples of each material were measured.The attenuation decibels per millimeter was then calculated by ratioingthe amplitude values obtained at different separation distances.

Optical density values in the Examples were obtained on a PacificSpectrograph Color System. The system consists of two major components,an optical sensor and a data terminal. The optical sensor employs a 6inch integrating sphere to provide diffuse illumination and 8 degreesviewing. This sensor can be used to measure both transmission andreflectance samples. When reflectance samples are measured, a specularcomponent may be included. A high resolution, full dispersion, gratingmonochromator was used to scan the spectrum from 380 to 720 nanometers.The data terminal features a 12 inch CRT display, numeric keyboard forselection of operating parameters and the entry of tristimulus values,and an alphanumeric keyboard for entry of product standard information.

Viscosity values in the Examples were measured at 150° C. with a StressRheometer, obtained from Cari-Med, Model CSL 100. All experiments wereperformed at a shear rate of 1,250 s⁻¹.

Crease values in the Examples were measured on solid area images printedon paper by (a) folding inwards the printed area of the image, (b)passing over the folded image a standard TEFLON® coated copper roll 2inches in width, 3 inches in outer diameter, 2.25 inches in innerdiameter, and weighing 860 grams, (c) unfolding the paper and wiping theloose ink from the creased imaged surface with a cotton swab, and (d)measuring the average width of the ink free creased area with an imageanalyzer.

Haze values in the Examples were measured on images printed on uncoatedpolyester (such as MYLAR®) with a Haze meter XL-211, HAZEGARD® System,obtained from Pacific Scientific Company.

The hardness values in the Examples were measured with a Digital-Pencilstyle Durometer, Model 211B-00 PTC, obtained from Pacific TransducerCorporation, using ASTM Standard specifications for resistance topenetration with a conical (30 degrees included angle) indenter andapplying a 1 kilogram load. The hardness range for materials as measuredwith this instrument is from about 1 to about 100, the latter being thehighest measurable value, Conductivity values in the Examples weremeasured under melt conditions at 150° C. by placing an aluminumelectrode in the melt and reading the resistivity output on a GenRad1689 precision RLC Digibridge at a frequency of 1 kilohertz.Conductivity was calculated from the resistivity data.

The gloss values in the Examples were obtained on a 75° Glossmeter,Glossgard II, obtained from Pacific Scientific (Gardner/NeotecInstrument Division).

The spherulite sizes in the Examples were measured with an opticalmicroscope with cross polarized light.

Lightfast values in the Examples were measured in a Mark V LightfastTester, obtained from Microscal Company, London, England.

Waterfast values in the Examples were obtained from the optical densitydata recorded before and after washing the images with water at 25° C.for five minutes.

EXAMPLE I

A black phase change ink was prepared by mixing 15 percent by weightpolyethylene monoalcohol (polymeric binder, Mn=700; viscosity at 150° C.7.9 centipoise; melting point 110° C.; hardness value 78.5; Aldrich44,448-0), 45 percent by weight 4-hydroxy-3-methoxy benzyl alcohol(viscosity modifier; hardness value 83.4; acoustic loss value 27decibels per millimeter; melting point 115° C.; Aldrich 17,553-6), 30percent by weight of a conductive complex of 4,4′-methylene bis(2,6-dimethylaniline) (present in an amount of 15 percent by weight ofthe ink; melting point 122° C.; Aldrich 36,079-1) with p-toluenesulfonicacid monohydrate (present in an amount of 15 percent by weight of theink: melting point 105° C.; conductivity 7.5 log(picomho/cm); Aldrich40,288-5), 5 percent by weight tetrakis(2,4-ditert butylphenyl)-4,4′-biphenyl diphosphonite (antioxidant; hardness value 90;Aldrich 46,852-5), and 5 percent by weight Neozapon Black X51 dye (C.I.Solvent Black; C.I. 12195; obtained from BASF). The resulting mixturewas heated to a temperature of about 140° C. and stirred for a period ofabout 60 minutes until it formed a homogeneous solution, followed bycooling the solution to 25° C. The resulting black ink exhibited ahardness value of 78.5 at 23° C. with an acoustic loss value of 58decibels per millimeter, a viscosity of 8.5 centipoise, and aconductivity of 6.9 log(picomho/cm) at 150° C.

EXAMPLE II

A blue phase change ink was prepared by mixing 15 percent by weightpolyethylene-block-poly(ethylene glycol) (polymeric binder, Mn=1400; 50percent by weight ethylene oxide; melting point 115° C.; Aldrich45,896-1), 45 percent by weight xylitol (viscosity modifier; acousticloss value 32 decibels per millimeter; melting point 96° C.; Aldrich85,158-2), 30 percent by weight of a conductive complex of4,4′-methylene bis(2,6-dimethylaniline) (present in an amount of 15percent by weight of the ink; melting point 122° C.; Aldrich 36,079-1)with 2,4-dinitrobenzene sulfonic acid dihydrate (present in an amount of15 percent by weight of the ink, melting point 108° C.; conductivity7.6log(picomho/cm); Aldrich 38,106-3), 5 percent by weight tetrakis(2,4-ditert butyl phenyl)-4,4′-biphenyl diphosphonite (antioxidant;hardness value 90; Aldrich 46,852-5), and 5 percent by weight Sudan Blue670 dye (C.I. #61554; obtained from BASF). The resulting mixture washeated to a temperature of about 140° C. and stirred for a period ofabout 60 minutes until it formed a homogeneous solution, followed bycooling the solution to 25° C. The resulting blue ink exhibited ahardness value of 79 at 23° C., an acoustic loss value of 58 decibelsper millimeter, a viscosity of 8.2 centipoise, and a conductivity of 6.7log(picomho/cm) at 150° C.

EXAMPLE III

A yellow phase change ink was prepared by mixing 15percent by weightoxidized polyethylene (polymeric binder; Mn=1300; viscosity at 125° C.225 centipoise; Aldrich 19,191-4), 45 percent by weight2,2-dimethyl-1-phenyl-1,3-propanediol (viscosity modifier; hardnessvalue 75; acoustic loss value 29 decibels per millimeter; melting point80° C.; Aldrich 40,873-5), 30 percent by weight of a conductive complexof 4,4′-methylene bis(2,6-dimethylaniline) (present in an amount of 15percent by weight of the ink; melting point 122° C.; Aldrich 36,079-1)with 2-propanesulfonic acid, sodium salt monohydrate (present in anamount of 15 percent by weight of the ink; melting point 81° C.;conductivity 7.4 log(picomho/cm); Aldrich 39,701-6), 5 percent by weighttetrakis (2,4-ditert butyl phenyl)-4,4′-biphenyl diphosphonite(antioxidant, hardness value 90; Aldrich 46,852-5), and 5 percent byweight Sudan Yellow 146 dye (C.I. #12700; obtained from BASF). Theresulting mixture was heated to a temperature of about 140° C. andstirred for a period of about 60 minutes until it formed a homogeneoussolution, followed by cooling the solution to 25° C. The resultingyellow ink exhibited a hardness value of 78 at 23° C., an acoustic lossvalue of 61 decibels per millimeter, a viscosity of 9.0 centipoise, anda conductivity of 6.8 log(picomho/cm) at 150° C.

EXAMPLE IV

A magenta phase change ink was prepared by mixing 15 percent by weightpoly(ethylene-co-acrylic acid) (polymeric binder; acrylic acid content20 percent by weight, hardness value 78.6; obtained from AldrichChemical Co., Milwaukee, Wis.), 45 percent by weight2,2′-(1,4-phenylenedioxy)diethanol (hardness value 82; acoustic lossvalue decibels per millimeter; melting point 102° C., Aldrich 23,791-4),30percent by weight of a conductive complex of 4,4′-methylenebis(2,6-dimethylaniline) (present in an amount of 15 percent by weightof the ink; melting point 122° C.; Aldrich 36,079-1) with hydroxymethanesulfinic acid monosodium salt dihydrate (present in an amount of 15percent by weight of the ink; melting point 70° C.; conductivity 7.2(log(picomho/cm); Aldrich 16,351-1), 5 percent by weighttetrakis(2,4-ditert butyl phenyl)-4,4′-biphenyl diphosphonite(antioxidant; hardness value 90; Aldrich 46,852-5), and 5 percent byweight Sudan Red 462 dye (C.I. #26050; obtained from BASF). Theresulting mixture was heated to a temperature of about 140° C. andstirred for a period of about 60 minutes until it formed a homogeneoussolution, followed by cooling the solution to 25° C. The resultingmagenta ink exhibited a hardness value of 78 at 23° C., an acoustic lossvalue of 57 decibels per millimeter, a viscosity of 8.3 centipoise, anda conductivity of 6.6log(picomho/cm) at 150° C.

EXAMPLE V

Each of the inks prepared as described in Examples I through IV wasincorporated into an acoustic ink jet printing test fixture utilizingthe ejection mechanism disclosed in J. Appl. Phys., 65(9), May 1, 1989,and references therein, the disclosures of each of which are totallyincorporated herein by reference. A jetting frequency of 160 MHz wasused to generate drops of about 2 picoliters, up to 12 drops per pixelat 600 spi. The images formed on paper exhibited excellent colorquality, hardness values of 79±1 at 23° C., optical density values of2.20 (black), 1.71 (cyan), 2.03 (magenta), 1.40 (yellow), crease valuesof 0.09 mm (black), 0.08 mm (magenta), 0.10 mm (cyan), 0.07 mm (yellow),and gloss values of 85 (black), 81 (magenta), 83 (cyan), 78 (yellow).The waterfastness and lightfastness values of these images were greaterthan 95 percent in all cases. The ink spherulite radius of the inks wasmeasured at 1 to 3 microns, leading to haze values of 13 to 18 whenprinted on transparency substrates.

EXAMPLE VI

A black phase change ink was prepared by mixing 15 percent by weightpolyethylene monoalcohol (polymeric binder; Mn=700; viscosity at 150° C.7.9 centipoise; melting point 110° C.; hardness value 78.5, Aldrich44,448-0), 45 percent by weight2,2-bis(hydroxymethyl)-2,2′,2″-nitrilotriethanol (viscosity modifier;hardness value 82.2; melting point 130° C.; Aldrich 15,666-3), 30percent by weight of a conductive complex of 4,4′-methylenebis(2,6-diisopropyl-N,N-dimethylaniline) (present in an amount of 15percent by weight of the ink; melting point 120° C.; Aldrich 40,353-9)with p-toluenesulfonic acid monohydrate (present in an amount of 15percent by weight of the ink; melting point 105° C.; conductivity 7.45log(picomho/cm); Aldrich 40,288-5), 5 percent by weighttetrakis(2,4-ditert butyl phenyl)-4,4′-biphenyl diphosphonite(antioxidant; hardness value 90; Aldrich 46,852-5), and 5 percent byweight Neozapon Black X51 dye (C.I. Solvent Black; C.I. #12195; obtainedfrom BASF). The resulting mixture was heated to a temperature of about140° C. and stirred for a period of about 60 minutes until it formed ahomogeneous solution, followed by cooling the solution to 25° C. Theresulting black ink exhibited a hardness value of 80 at 23° C., anacoustic loss value of 59 decibels per millimeter, a viscosity of 8.6centipoise, and a conductivity of 6.85 log(picomho/cm) at 150° C.

EXAMPLE VII

A blue phase change ink was prepared by mixing 15 percent by weightpolyethylene-block-poly(ethylene glycol) (polymeric binder, Mn=1400: 50percent by weight ethylene oxide; melting point 115° C.; Aldrich45,896-1), 45 percent by weight di(trimethylolpropane) (viscositymodifier, hardness value 85.8; acoustic loss value 35 decibels permillimeter, melting point 111° C.; Aldrich 41,613-4), 30 percent byweight of a conductive complex of 4,4′-methylenebis(2,6-diisopropyl-N,N-dimethylaniline) (present in an amount of 15percent by weight of the ink; melting point 120° C.; Aldrich 40,353-9)with 2,4-dinitrobenzene sulfonic acid dihydrate (present in an amount of15 percent by weight of the ink; melting point 108° C.: conductivity7.5log(picomho/cm); Aldrich 38,106-3), 5 percent by weighttetrakis(2,4-ditert butyl phenyl)-4,4′-biphenyl diphosphonite(antioxidant: hardness value 90; Aldrich 46,852-5), and 5 percent byweight Sudan Blue 670 dye (C.I. #61554; obtained from BASF). Theresulting mixture was heated to a temperature of about 140° C. andstirred for a period of about 60 minutes until it formed a homogeneoussolution, followed by cooling the solution to 25° C. The resulting blueink exhibited a hardness value of 81 at 23° C., an acoustic loss valueof 59 decibels per millimeter, a viscosity of 8.3 centipoise, and aconductivity of 6.65 log(picomho/cm) at 150° C.

EXAMPLE VIII

A yellow phase change ink was prepared by mixing 15percent by weightpolyethylene monocarboxylic acid (polymeric binder: hardness value 78.7;Aldrich 40,706-2), 45 percent by weight 4,4′-trimethylenebis(1-piperidine ethanol) (viscosity modifier; hardness value 78;acoustic loss value 28 decibels per millimeter; melting point 96° C.:Aldrich 12,122-35), 30 percent by weight of a conductive complex of4,4′-methylene bis(2,6-diisopropyl-N,N-dimethylaniline) (present in anamount of 15 percent by weight of the ink; melting point 120° C.;Aldrich 40,353-9) with 2-propanesulfonic acid, sodium salt monohydrate(present in an amount of 15 percent by weight of the ink; melting point81° C.; conductivity 7.35 log(picomho/cm); Aldrich 39,701-6), 5 percentby weight tetrakis(2,4-ditert butyl phenyl)-4,4′-biphenyl diphosphonite(antioxidant; hardness value 90; Aldrich 46,852-5), and 5 percent byweight Sudan Yellow 146 dye (C.I. #12700; obtained from BASF). Theresulting mixture was heated to a temperature of about 140° C. andstirred for a period of about 60 minutes until it formed a homogeneoussolution, followed by cooling the solution to 25° C. The resultingyellow ink exhibited a hardness value of 77.5 at 23° C., an acousticloss value of 62 decibels per millimeter, a viscosity-of 9.1 centipoise,and a conductivity of 6.75 log(picomho/cm) at 150° C.

EXAMPLE IX

A magenta phase change ink was prepared by mixing 15 percent by weightpoly(ethylene-co-acrylic acid) (polymeric binder; acrylic acid content20 percent by weight; hardness value 78.6; obtained from AldrichChemical Co., Milwaukee, Wis.), 45 percent by weightN-methyl-D-glucamine (viscosity modifier, hardness value 83.2; acousticloss value 30 decibels per millimeter; melting point 130° C.; AldrichM4,700-0), 30 percent by weight of a conductive complex of4,4′-methylene bis(2,6-diisopropyl-N,N-dimethylaniline) (present in anamount of 15 percent by weight of the ink; melting point 120° C.;Aldrich 40,353-9) with hydroxymethane sulfinic acid monosodium saltdihydrate (present in an amount of 15 percent by weight of the ink,melting point 70° C.; conductivity 7.25 log(picomho/cm); Aldrich16,351-1), 5 percent by weight tetrakis(2,4-ditert butylphenyl)-4,4′-biphenyl diphosphonite (antioxidant; hardness value 90;Aldrich 46,852-5), and 5 percent by weight Sudan Red 462 dye (C.I.#26050; obtained from BASF). The resulting mixture was heated to atemperature of about 140° C. and stirred for a period of about 60minutes until it formed a homogeneous solution, followed by cooling thesolution to 25° C. The resulting magenta ink exhibited a hardness valueof 80 at 23° C., an acoustic loss value of 58 decibels per millimeter, aviscosity of 8.35 centipoise, and a conductivity of 6.55 log(picomho/cm)at 150° C.

EXAMPLE X

Each of the inks prepared as described in Examples VI through IX wasincorporated into an acoustic ink jet printing test fixture utilizingthe ejection mechanism disclosed in J. Appl. Phys., 65(9), May 1, 1989,and references therein, the disclosures of each of which are totallyincorporated herein by reference. A jetting frequency of 160 MHz wasused to generate drops of about 2 picoliters, up to 12 drops per pixelat 600 spi. The images formed on paper exhibited excellent colorquality, with hardness values of 79±2 at 23° C., optical density valuesof 2.10 (black), 1.67 (cyan), 2.01 (magenta), 1.41 (yellow), creasevalues of 0.11 mm (black), 0.09 mm (magenta), 0.12 mm (cyan), 0.09 mm(yellow), and gloss values of 84 (black), 82 (magenta), 82 (cyan), 79(yellow). The waterfastness and lightfastness values of these imageswere greater than 90 percent in all cases. The ink spherulite radius ofthe inks was measured at 1 to 3 microns, leading to haze values of 13 to18 when printed on transparency substrates.

Other embodiments and modifications of the present invention may occurto those of ordinary skill in the art subsequent to a review of theinformation presented herein; these embodiments and modifications, aswell as equivalents thereof, are also included within the scope of thisinvention.

What is claimed is:
 1. An ink composition comprising (a) a polyethylenehomopolymer or copolymer binder having a melting point of from about 60to about 150° C., (b) a nonpolymeric alcohol viscosity modifier having amelting point of from about 60 to about 150° C. which is (1)2-hydroxybenzyl alcohol, (2) 4-hydroxybenzyl alcohol, (3) 4-nitrobenzylalcohol, (4) 4-hydroxy-3-methoxy benzyl alcohol, (5)3-methoxy-4-nitrobenzyl alcohol, (6) 2-amino-5-chlorobenzyl alcohol, (7)2-amino-5-methylbenzyl alcohol, (8) 3-amino-2-methylbenzyl alcohol, (9)3-amino-4-methyl benzyl alcohol, (10) 2(2-(aminomethyl)phenylthio)benzylalcohol, (11) 2,4,6-trimethylbenzyl alcohol, (12)2-amino-2-methyl-1,3-propanediol, (13) 2-amino-1-phenyl-1,3-propanediol,(14) 2,2-dimethyl-1-phenyl-1,3-propanediol, (15)2-bromo-2-nitro-1,3-propanediol, (16) 3-tertbutylamino-1,2-propanediol,(17) 1,1-diphenyl-1,2-propanediol, (18) 1,4-dibromo-2,3-butanediol, (19)2,3-dibromo-1,4-butanediol, (20) 2,3-dibromo-2-butene-1,4-diol, (21)1,1,2-triphenyl-1,2-ethanediol,. (22) 2-naphthalenemethanol, (23)2-methoxy-1-naphthalenemethanol, (24) decafluoro benzhydrol, (25)1-benzeneethanol, (26) 4,4′-isopropylidene bis(2-(2,6-dibromophenoxy)ethanol), (27) 2,2′-(1,4-phenylenedioxy)diethanol, (28)2,2′-bis(hydroxymethyl)-2,2′,2″-nitrilotriethanol, (29)di(trimethylolpropane), (30) 2-amino-3-phenyl-1-propanol, (31)tricyclohexylmethanol, (32) tris(hydroxymethyl)aminomethane succinate,(33) 4,4′-trimethylene bis(1-piperidine ethanol), (34) N-methylglucamine, (35) xylitol or mixtures thereof, (c) a colorant, (d) anoptional conductivity enhancing agent, (e) an optional antioxidant, and(f) an optional UV absorber.
 2. An ink composition according to claim 1wherein the binder is a polyethylene monoalcohol, apolyethylene-block-poly(alkylene glycol), an oxidized polyethylene, apolyethylene monocarboxylic acid, a copolymer of ethylene and anunsaturated acid, or a mixture thereof.
 3. An ink composition accordingto claim 1 wherein the binder is a polyethylene-block-poly(ethyleneglycol), a poly(ethylene-co-acrylic acid), apoly(ethylene-co-methacrylic acid), or a mixture thereof.
 4. An inkcomposition according to claim 1 wherein the binder is present in theink in an amount of at least about 5 percent by weight of the ink, andwherein the binder is present in the ink in an amount of no more thanabout 30 percent by weight of the ink.
 5. An ink composition accordingto claim 1 wherein the viscosity modifier is present in the ink in anamount of at least about 30 percent by weight of the ink, and whereinthe viscosity modifier is present in the ink in an amount of no morethan about 55 percent by weight of the ink.
 6. An ink compositionaccording to claim 1 wherein the colorant is a dye.
 7. An inkcomposition according to claim 1 containing a conductivity enhancingagent which is a complex of (a) an amine and (b) either (i) asulfur-containing acid or acid salt or (ii) a phosphorus-containingcompound.
 8. An ink composition according to claim 7 wherein the amineis an alkyl amine, an aniline, a dianiline, a bis dianiline, or amixture thereof.
 9. An ink composition according to claim 7 wherein theamine is (1) 4-(hexadecylamino)benzylamine, (2)N-octanoyl-N-methyl-glucamine, (3) octanoic hydrazide, (4) 4-hexadecylsulfonyl aniline, (5) 2,2′-dithio dianiline, (6) 4,4′-dithiodianiline,(7) 3,3′-methylene dianiline, (8) 4,4′-methylene dianiline, (9)N-methyl-4,4′-methylene dianiline, (10) 4,4′-methylene bis(2,6-diethylaniline), (11) 4,4′-methylene bis(2,6-diisopropyl-N, N-dimethylaniline),(12) 4,4′-methylene bis(N,N-dimethylaniline), (13) 4,4′-methylenebis(2,6-dimethylaniline), (14) 4,4′-methylenebis(3-chloro-2,6-diethylaniline), (15) 3,3′-(sulfonylbis(4,1-phenylene))dianiline, (16) 4,4′-(1,3-phenylene diisopropylidene)bisaniline, or mixtures thereof.
 10. An ink composition according toclaim 7 wherein the sulfur-containing acid or acid salt is a sulfonicacid, a sulfonic acid salt, a sulfinic acid, a sulfinic acid salt, or amixture thereof and wherein the phosphorus-containing compound is aphosphinic acid, a phosphonic acid, or a mixture thereof.
 11. An inkcomposition according to claim 7 wherein the sulfur-containing acid oracid salt is (1) 2,4-dinitrobenzene sulfonic acid, (2) 2-propanesulfonicacid salt, (3) p-toluenesulfonic acid, (4) hydroxymethane sulfinic acidsalt, or a mixture thereof and wherein the phosphorus-containingcompound is (i) phenylphosphinic acid, (ii) dimethylphosphinic acid,(iii) methyl phosphonic acid, or mixtures thereof.
 12. An inkcomposition according to claim 1 containing a conductivity enhancingagent in an amount of at least about 4 percent by weight of the ink, andcontaining a conductivity enhancing agent in an amount of no more thanabout 40 percent by weight of the ink.
 13. An ink composition accordingto claim 1 wherein the ink has a hardness value of at least about 70 attemperatures of from about 20 to about 25° C.
 14. An ink compositionaccording to claim 1 wherein the ink has a melting point of no lowerthan about 60° C., and wherein the ink has a melting point of no higherthan about 150° C.
 15. An ink composition according to claim 1 whereinthe ink has a haze value of no more than about
 25. 16. A process whichcomprises incorporating into an ink jet printing apparatus an inkcomposition according to claim 1, melting the ink, and causing dropletsof the melted ink to be ejected in an imagewise pattern onto a printsubstrate.
 17. A process according to claim 16 wherein the printingapparatus employs an acoustic ink jet process, wherein droplets of theink are caused to be ejected in imagewise pattern by acoustic beams. 18.A process according to claim 16 wherein the printing apparatus employsan acoustic ink jet printing process wherein droplets of the ink areformed by acoustic beams without imparting a substantial velocitycomponent toward the print substrate, using a droplet forming force thatis sufficient only to form the ink droplets, and wherein the printingprocess further comprises generating an electric field to exert anelectrical force different from the droplet forming force on the inkdroplets to move the ink droplets toward the print substrate, andcontrolling the electrical force exerted on the formed complete inkdroplets by the electric field.
 19. A process according to claim 16wherein the printing apparatus employs a piezoelectric ink jet process,wherein droplets of the ink are caused to be ejected in imagewisepattern by oscillations of piezoelectric vibrating elements.